Photo by Adobe Stock/Jim Ekstrand
Two days of rain kept me from some much-needed mowing, but I thought it would be a good opportunity to work on a couple of projects in my shop. When I turned on the lights, though, my eyes drifted to a dark spot on the ceiling; the dreaded first sign of a leaky roof.
The roof on my shop was covered with asphalt shingles that were more than 20 years old. I’d been thinking about replacing the sorry-looking ones for the last two years, but I’d put it off as a project that would take a lot of time and money. After spotting the early signs of damage caused by a leaking roof, I wished I’d replaced it earlier.
With a pit in my stomach, I removed a blemished section of drywall to assess the damage. Thankfully, other than the area directly above the leak, the rest of the roof looked dry. After going up on the roof for a thorough examination, it became obvious the shingles were in poor condition and in need of replacement.
The leak that prompted my inspection appeared to be close to one of the roof vents. The sealant around the vent to keep moisture from getting under the shingles was worn and missing in some areas. Its weathering probably contributed significantly to the leak. I had no doubt the roof repair I’d put off was long overdue.
A Costly Choice
I began considering roof replacement options and quickly discovered I’d need to make several decisions. The first — and quite possibly the most important decision — was whether to use asphalt shingles or some type of metal roofing. Either roofing material has advantages and disadvantages that need to be considered for each situation.
The price of materials is always an important factor for me when making a decision, but upfront costs can be deceiving. Asphalt shingles can cost less than half as much as metal roofing. While metal’s upfront costs may be more significant than asphalt’s, metal roofing can last up to three times longer, making it an economical option. Here are some considerations when choosing between these roofing materials.
Asphalt shingles are made up of fiberglass sandwiched between asphalt and ceramic granules. They come in a variety of styles and are usually affordable, even for a tight budget. They’re relatively small and are packaged in bundles, making them easy to handle. Each bundle will cover about 33 square feet.
Shingles are usually ordered by the “square,” which is 100 square feet (or three bundles). To determine how many shingles you’ll need for your roof, calculate the square footage by multiplying the length and width of your roof. Next, divide the square footage by 100 to get the total number of squares needed.
Pricing for asphalt shingles varies by region and supplier, but the cost of a square of basic shingles at big-box home improvement stores ranges from $100 to $175. Other material costs are also involved, such as nails and underlayment (which goes between the roof and the shingles). In summary, the benefits of asphalt shingles include:
- Lower upfront cost compared with metal roofing
- Variety of colors and styles
- Noise dampening effect on roof
- Generally easier to install and repair than metal roofing
- Fair lifespan: 15 to 30 years, depending on type and quality
While asphalt shingles have their advantages, they’re also more susceptible to damage. Persistent moisture leads to algae and fungus growth on the shingles, which may cause premature failure. Shingles aren’t the best choice in areas with a hot climate, as they absorb heat and can transfer it to the interior of the structure.
Illustration by Brad Anderson
Metal roofing has been a staple in rural communities for generations. From pole barns to loafing sheds, metal is an established standard for sheathing and roofing farm buildings. This popularity stems from its ability to shed rain and snow and withstand strong winds. In recent years, metal’s popularity has soared in the housing market due to technological developments in the industry, which have made it more affordable, environmentally friendly, and visually pleasing.
One of the biggest advantages of metal roofing is its longevity. A properly installed metal roof can last 50 years or more, making it the only roof your structure may need during your lifetime. If you’ve needed to replace an asphalt roof a few times during the life of your building, you know that metal roofing will provide a greater return on investment. Costs for metal roofing vary widely, but standard metal sheeting — normally 36 inches wide — can be ordered in lengths from 6 to 40 feet. An average cost for a 10-foot-by-36-inch-wide panel runs between $25 and $75, depending on type and quality.
Metal roofing is usually ordered based on the roof surface’s total square footage. Another nice feature of ordering metal roofing panels is that many companies will sell a panel based on the specific length you need for your roof. If the vertical length of the roof from peak to eave is 9-1⁄2 feet long, these companies will cut the number of panels needed to that specific length so you won’t have to do it. To summarize their benefits, metal panels:
- Reflect solar heat to significantly reduce cooling costs
- Are more fire resistant than shingles
- Can withstand heavy windstorms and hail that would tear off asphalt
- Can last 50 years or more
Metal roofing also has some drawbacks. In addition to being more expensive than asphalt shingles, metal roofing’s installation process is more complicated and requires unique tools and prior experience.
Noise may be a factor if the roof isn’t insulated, or if there’s no underlayment. Also, regardless of the manufacturer’s guarantee, your metal panels will fade with time. Color matching becomes an issue if you have to replace a panel later.
A Roof with Some Mettle
Because my shop is detached and relatively small (24 by 16 feet), and I’m located in a rural area, I knew not many roofers would be interested in the job. So, I decided to do the work myself.
I settled on a metal roof because the panels would be easy for me to handle on my own. Using metal would also reduce the amount of labor, as the panels could be installed on top of my building’s existing shingles. (Placing metal panels over the shingles doesn’t dramatically increase the roof load compared with another layer of shingles, as they’re much lighter than shingles.)
I visited a few home improvement retail stores and decided to use the store that worked closely with a supplier who allowed custom-sized metal roof panels at no extra charge. After measuring the distance from the ridge of my roof to the eave, I settled on a panel length of 8 feet 10 inches by 36 inches wide, allowing for a 2-inch overhang on the eaves. I needed 17 panels, a ridge cap, and approximately 200 residential self-tapping roofing screws to complete my new metal roof.
Photo by Tim Nephew
When I was notified that my custom order had arrived, I hooked up a trailer and picked it up. The panels were shipped on a custom pallet that I was charged for but allowed to return for full credit when I returned it to the store. Each panel weighed 22 pounds, and they were easy to handle, so I was able to move them myself.
Photo by Tim Nephew
Since I heat my shop when I’m working inside, I knew I needed roof venting. Roof venting prevents damaging moisture and heat buildup in the attic. Previously, with my shingled roof, I used plastic roof vents to bring air into the attic area. While you can use individual vents on metal roofs, I elected instead to cut a ridge vent the length of my shop for better overall ventilation. To cut the roof vent, I removed the shingles covering the ridge cap. Using a circular saw, and being careful not to cut into a roof joist, I cut a 2-inch piece of wood from the roof sheeting.
Photo by Tim Nephew
Next, I installed the 30-pound underlayment directly on top of the existing shingles. The underlayment masks the shape of the existing shingles that can show through once the metal panels are installed, and it adds an additional water barrier. Underlayment is fairly easy to roll out and, using a hammer tacker, to staple down to existing shingles.
With the overlay in place, I started installing the metal panels. The panels are installed vertically. If your roof is square, the panels will run square. To check if your roof plane is true, simply run a measuring tape diagonally from top to bottom across one side of the roof to get a measurement, and then repeat the process with the opposite corners of the roof. If your diagonal measurements are equal, your roof is square. If you find your roof isn’t quite square, you may have to compensate as you install the new roof by adjusting the panels to make them true to the eaves instead of the rakes (the slanting edges of a gable-style roof).
Photo by Tim Nephew
Once you’ve laid and adjusted your first panel, the second panel should overlap the previous panel and be flush at the eaves. On exposed fastener panels, the overlap should always be fastened top to bottom to ensure a good overlapping of the panels.
Photo by Tim Nephew
When all the panels have been installed, you’ll need to install the ridge cap to cover the vent that was cut in your roof to block moisture while still allowing airflow. The ridge cap may have mesh underneath that’s designed to keep out pests. Some ridge vents require that you install a mesh vent on top of the panels before you place the ridge cap.
To give a shingled roof a finished look, you may wish to install hemmed J channel along the gabled end and on the eaves. To install the trim, nail it down on top of the existing shingles. Then, apply a strip of tape mastic (sticky two-sided tape) on top of the trim. Finally, install the metal panels over the trim. Depending on the finished look you have in mind, you could also add fascia to the rake sides of the roof.
Photo by Tim Nephew
Regardless of how you decide to trim your building, you’ll want to install closure strips under the bottom edge of the panels on the bottom row. These foam strips are die cut to match the panel profiles, and they have adhesive on the bottom that adheres to the J trim. The closure strips provide a protective barrier against critters, such as bats, and they’re made of closed-cell foam that won’t absorb moisture.
Rough Roofin’ Tools
Here’s a list of tools you may find useful if you plan on doing your own metal roofing work. Even if you purchase pre-cut panels, you’ll need to cut panels and trim.
- Tin snips
- Metal shears
- Panel shears
- Tape measure
- Cordless impact driver (for fasteners)
Note: Most metal roofing manufacturers recommend that you don’t use a circular saw to cut panels. Regardless of the type of blade used, cuts made with the saw may cause premature rusting and paint peeling at the cut point.
Set Up Shop
I decided to tackle my roofing job myself because it wasn’t a large project and I have decent carpentry skills. I also feel comfortable climbing on roofs and already own most of the tools necessary to complete the job. I don’t want to minimize the labor involved to complete a job like this, or the potential for falls and other serious accidents. If you don’t feel comfortable doing a roofing project yourself, look in your area for qualified roofing companies.
A regular GRIT contributor, Tim Nephew lives in rural Minnesota, where he owns and maintains 80 acres of wildlife habitat.